Prognostic value of layer-specific global longitudinal strain in patients undergoing coronary artery bypass grafting

Background

Recent improvements in speckle tracking echocardiography have made sectionalized quantification of layer-specific global longitudinal strain (GLS) possible. Prior studies have reported prognostic value of GLS in several cardiac diseases, however, the use of layer-specific strain has not been investigated in patients undergoing coronary artery bypass grafting (CABG).

Purpose

To determine the prognostic value of layer-specific GLS for predicting all-cause mortality after CABG.

Methods

In this retrospective cohort study, consecutive patients undergoing isolated CABG between 2006 and 2011 were included. The patients were followed through nation-wide registries for the endpoint of all-cause mortality. Multivariable Cox regression models adjusted for clinical and echocardiographic baseline characteristics were used to assess the association between layer-specific GLS and all-cause mortality. Cumulative survival was stratified by clinical age and gender-dependent cut-off values for the layer-specific GLS, which was obtained from a large healthy population study.

Results

Of 641 patients included (mean age 67 years, 84% male), 70 (10.9%) died during follow-up (median 3.8 years [IQR: 2.7; 4.9 years]). Patients who died during follow-up were significantly older (71 years vs. 67 years, P = <0.001) and had a lower LVEF (46% vs. 51% P = <0.001). Endocardial GLS (GLSendo) (−14.2% vs. −16.3%, P<0.001), whole wall GLS (−12.1% vs. −13.9%, P<0.001), and epicardial GLS (GLSepi) (−10.6% vs. −12.2%, P<0.001) were all reduced in patients who died during follow-up, and patients with GLS below cut-off had a more than two-fold increased risk of all-cause mortality (Figure 1). The risk of dying increased linearly with decreasing absolute GLS for all layers (p<0.0002 for all layers), (Figure 2). In multivariable models, all layer-specific strain parameters remained significantly associated with all-cause mortality; GLSepi: HR=1.14 (1.05–1.23), p=0.002; GLS: HR=1.12 (1.04–1.20), p=0.002; GLSendo: HR=1.09 (1.03–1.16), p=0.003, per 1% absolute decrease. However, only GLSepi remained significantly associated with mortality when also adjusting for echocardiographic parameters (GLSepi: HR=1.12 (1.00–1.25), p=0.049, per 1% absolute decrease) and separately also after adjusting for the EuroScore II (GLSepi: HR=1.09 (1.00–1.18), p=0.043, per 1% absolute decrease).

Conclusion

Layer-specific GLS is an independent prognosticator of all-cause mortality after CABG. In multivariable models, GLSepi provided significant prognostic value after adjusting for echocardiographic parameters and EuroScore II.

Funding Acknowledgement

Type of funding sources: Public hospital(s). Main funding source(s): Research grant from Herlev & Gentofte University Hospital's internal research funds. Figure 1. Kaplan-Meier survival estimatesFigure 2. Incidence rate of all-cause mortality